Coastal wetlands play a vital role in carbon (C) sequestration, named ‘blue carbon’, but mechanisms associated with the C sequestration are complex and not always well understood. Global climate change, sea level rise, land-use change, and environmental pollution could also add many unpredictable uncertainties to the potentials of C sequestration of coastal zone in future.
The review provided an overview of C processes, including input, output, and deposition, in coastal wetlands (Fig. 1). However, long-term (hundreds to thousands of years) and accurate assessment of C storage in coastal wetlands is needed, with particular emphasis on deeper soil profiles or sediments. For example, the role of C occluded in diatoms and phytoliths as critical long-term C sequestration pathways in coastal ecosystems required further studies. We then summarized the impacts of different factors on C processes by modifying soil physicochemical properties, plant growth, vegetation type, and microbial community composition. Among these factors, we analyzed the effects of climate warming and nitrogen input (Fig. 2), which exert significant effects on C processes but which are not adequately explained in the previous literature. A slight warming trend can initially enhance C storage in the short-term, prolonged, while significant warming may ultimately lead to a decrease in C storage because of enhanced C decomposition. The effects N addition vary based on factors such as N content, N forms, and the duration of experiments. Nevertheless, short-term studies consistently illustrate positive effects of N addition on vegetation growth. Among other factors, drought, increased salinity, and inundation are environmental stressors that can significantly restrain vegetation growth and C input. Extreme climate events and human activities, such as reclamation and vegetation harvesting, have detrimental effects on C storage by damaging coastal wetlands and suppressing vegetation. Finally, this study also illustrates various coastal wetland restoration methods aimed at enhancing C sequestration, including legal frameworks, scientific theories, vegetation management, hydrological restoration, and other relevant constructions. Quantifying the costs and benefits associated with different restoration methods could help to optimize the ecosystem services of coastal wetlands.
Fig. 1. (a) Conceptual diagram illustrating carbon cycles in coastal wetlands, encompassing carbon input, output, and deposition. (b) The influence of vegetation and microorganism on carbon sequestration in coastal wetlands.
Fig. 2. The effects of climate warming (a) and N addition (b) on organic carbon processes in coastal vegetated wetlands. “***” represented p < 0.001 and “**” represented p < 0.01 of the differences between control and warming/N addition experiments.
This review offers valuable theoretical support and scientific references for the sustainable development and management of coastal wetlands in a changing climate. This study has been published in the Earth-Science Reviews. The first author is associate Prof. Hao Qian and the corresponding author is Prof. Song Zhaoliang and Dr. Zhang Xiaodong.
https://www.sciencedirect.com/science/article/pii/S0012825224001806
